Optimality of single-carrier zero-padded block transmissions

We consider the class of linear precoded (LP) orthogonal frequency division multiplexing (OFDM) systems. We first show that single-carrier zero-padded transmissions, termed ZP-only, can be viewed as a special case of LP-OFDM. By resorting to the pair-wise error probability analysis, we establish the optimality of ZP-only among the LP-OFDM class in terms of its performance in random frequency-selective channels. It is shown that ZP-only enjoys maximum diversity and coding gains. We also consider various decoding options for ZP-only, and compare them in terms of performance and complexity.